Escapement mechanism for clockwork fuzes



Jam 17, 1967 D. e. COLLINS ETAL 3,298,310

ESCAPEMENT MECHANISM FOR CLOCKWORK FUZES Filed Oct. 14, 1964 3Sheets-Sheet l INVENTORS DONALD G. COLLINS JOHN SEIFNER CLARENCE W.WANDREY ATTORNEYS Jan. 17"

, 1967 D. 5. COLLINS ETAL 3,298,310

ESCAPEIVIEIIIT MECHANISM FOR CLOCKWORK FUZES Filed Oct. 14, 1964 3Sheets-Sheet 2 INVEN TOR S DONALD G. COLLINS JOHN SEIFNER CLARENCE W.WANDRE Y QLC ATTORNEYS n- 1967 D. G. COLLINS- ETAL 3,

ESCAPEMENT MECHANISM FOR CLOCKWORK FUZES Filed'Oct. 14, 1964 sSheets-Sheet a INVENTORS DONALD G. COLLINS JOHN SE/FNER CLARENCE W.WANDREY x' W ATTO NEYS United States Patent 3,298,310 ESCAPEMENTMECHANISM FOR CLOCKWORK FUZES Donald G. Collins, Deerfield, Mass., andJohn Serfner,

Chicago, and Clarence W. Wandrey, Wheaton, Ill., assignors, by mesneassignments, to the United States of America as represented by theSecretary of the Army Filed Oct. 14, 1964, Ser. No. 403,957 1 Claim.(Cl. 102-84) This invention relates to improvements in escapementmechanisms and, more specifically, to a simplified time delay escapementmechanism for use with fuze armmg devices.

Fuzes which contain mechanisms to delay the arming of the fuze after aprojectile has been fired to insure the safety of the person firing theprojectile are well known and take a variety of different forms. Oneconventional method of providing an added time delay for a f-uzeinvolves the use of a driving element, such as a pinion or escape wheel,rigidly attached to a spring-driven rotor, and .a mating driven element,such as a gear or pallet mounted on a stator portion of the fuze proper,which is usually the rotor housing. This conventional approach, however,creates a need for very close mechanical tolerances. which is notcompatible with the loose assembly tolerances normally provided forassembling a rotor to a fuze.

Another common expedient for providing a substantial time delay in fuzesrequires the use of a gear train to provide sutficient angulardisplacement of an escape wheel. In such time delay escapementmechanisms, a first gear is usually affixed to the rotor shaft, and apinion meshes with this gear to provide the necessary rotary motion toan escape wheel. The escape wheel then meshes with a pellet pivoted to.operate in an oscillatory motion, thus providing in combination, therequired delay. However, the space requirements for these additionalcomponents require modifications to the basic fuze to keep within theexisting fuze dimensions. Also, to maintain the necessary rotor torque,a thicker rotor spring is often necessary, which also adds to the spacerequirements.

In designing a fuze for projectile use it is important to have a certainminimum arming distance. The arming distance is normally considered tobe the distance a projectile travels from the time it is fired to thetime it is armed, jor ready to be exploded. With projectiles or shellshaving large muzzle velocities, a substantial time delay before armingis not of great importance because a safe distance is quickly achieved.However, with shells having smaller muzzle velocities, it is veryimportant to provide a time delay sufiicient to allow the shell totravel a minimum safe distance before it is armed. Such a time delayprotects the person expending the shell and is necessary to meet minimumarming distances specified for particular shells.

In order to increase the time for arming a fuze after firing, it hasbeen suggested to use a setback-arming device having a sequential leafsystem to permit a projectile to get beyond a safe distance before it isarmed. The static arming time of such a system usually works wellwithhigher muzzle velocity projectiles but is inadequate. for low andintermediate muzzle velocity am- 3,298,310 Patented Jan. 17, 1967 ever,the time delay added by such increase in rotor travel is not sufficientto meet the minimum distance requirements for low muzzle velocityprojectiles.

Then, escapement mechanisms were introduced into the fuzes to increasethe time delay. As mentioned above, such added escapement systemsrequired more space than was generally available, and were also quitecomplex, expensive, as well as time consuming and difiicult tmanufacture. 7

As a result of the inadequacies of the present time delay systems, aneed has arisen to provide means for use with a fuze which is extremelysimple, has very low space requirements, and has a high degree ofruggedness. As far as possible, the machining costs for producing such atime delay in fuzes should be kept to a minimum, while maintaining highreliability. Further, such a time delay should be produced whichrequires little or no modification of the basic fuze design. Finally,the time delay mechanism should be able to withstand high accelerationswithout a degradation of performance.

In accordance with the present invention, novel means have been providedto permit a time delay of sufiicient magnitude for safe firing of lowmuzzle velocity projectiles. By virtue of the present invention, a fuzewould not be armed until the minimum safe distance has been covered.Also, the time delay escapement mechanism of the present inventionrequires very little space in the projectile.

It is accordingly a primary object of the present invention to providenovel time delay escapement means.

It is still another important object of the present invention to providea novel time delay escapement system which is simple and extremelyrugged.

It is a further object of the present invention to provide a novel timedelay escapement mechanism that provides a substantial time delay in asmaller space and with greater simplicity of design than is usual formechanisms providing time delays in this range.

It is still another important object of the present invention to providemechanical time delay means for fuzes which employ only an escape wheeland an oscillating member as the delay elements that act in conjunctionwith a three-quarter turn displacement of a spring-driven rotor.

It is a further important object of the present invention to providenovel time delay escapement means for explosive fuzes which makepossible sufiicient angular displacement of the escape wheel in a smalldevice with sufficient time delay, but without the use of a gear train.

It is still another object of the present invention to provide a ruggedtime delay escapement mechanism designed to assure proper componentorientation with a minimum of space and complexity.

It is a further object of the present invention to provide a time delayescapement mechanism of relatively few component parts requiring littlemodification in the basic design of the fuze with which it is used.

It is still another object of the present invention to provide a timedelay escapement mechanism for use with a fuze which can withstand highacceleration without performance degradation.

It is still a further object of the present invention to provide a timedelay escapement system for use with a fuze having a heavy rotor whereinthe combination produces a smoother rotation without disturbing theactual time delay resulting from the escapement wheel-pallet action.

These and other important objects and advantages of 3 the presentinvention will become more apparent in con,- nection with the ensuingdescription and appended claims, as Well as the attached drawingswherein:

FIGURE 1 is a front elevation view of the fuze and escapement mechanismemboding the principles of the present invention;

FIGURE 2 is a side elevation view of the fuze and escapement mechanismshown in FIGURE 1;

FIGURE 3 is a rear elevation view of the fuze and escapement mechanismshown in FIGURE 1;

FIGURE 4 is a sectional view of the fuze taken along the line 44 ofFIGURE 2;

FIGURE 5 is a partial enlarged section showing the time delay escapementmechanism of the present invention;

FIGURE 6 is a vertical sectional view on line 6-6 of FIGURE 5; and

FIGURE 7 is an exploded perspective view of the essential parts of thetime delay mechanism.

As previously indicated, the present invention involves novel time delayescapement means, and in particular, a time delay escapement mechanismfor fuzes used in projectiles.

The operation of the time delay escapement means of the presentinvention is based on an escape wheel-pallet principle. Preferably, theescape or star wheel is connected to a rotating member and is caused torotate a portion of a full turn. The pallet, which is essentially anoscillating mass, is designed to engage the teeth of the escape wheel toprovide the necessary time delay. The escape wheel is connected to aheavy mass which slows the acceleration of the escape wheel due to itsinertia, and the rotational inertia of the pallet also is high. Thepallet is provided with an opening a given distance from its axis ofpivot and two wedge-shaped teeth project into 'the opening in positionto engage the teeth of the escape wheel. Upon rotation of the starwheel, the pallet oscillates while the rotor inertia tends to maintainthe rotation smooth by alternately helping and hindering the action ofthe escape wheel and pallet combination without disturbing the actualtime delay. Thus, there is provided simple means for causing a timedelay. In addition to this broad concept, the present inventioncontemplates more specific concepts including the provision ofparticular structural elements which are peculiarly well adapted toeffect the broad objects of the present invention, as will be moreparticularly described hereinafter.

The basic fuze environment for the time delay escapement means of thepresent invention is best illustrated in FIGS. 1-4. As shown therein,and especially FIG. 2, the fuze proper consists of three minorsub-assemblies, namely, a spring driven rotor 10, a sequential-leaf setback release mechanism 12, and an arming delay mechanism 14. A rotorhousing assembly and an aluminum shield assembly, both of which are notshown for the sake of clarity, complete the fuze structure.

The rotor 10, which is a single machined piece, has a passageway 16 forreceiving an electric detonator which arms the fuze. As shown in FIG. 3,a spring biased pin 18 extends from the larger diameter portion of therotor to provide the electrical contact necessary between the electricdetonator and power source for fuze arming. A locking-pin slot 20 isformed in the rear face of the rotor 10 along with a blow-through hole22 leading to the passageway 16 in the rotor 10. The rotor 10 is mountedon a shaft 24 which extends through the release mechanism 12 and thearming delay mechanism 14. As shown in FIG. 1, the outer end of theshaft 24 is slotted to form a groove 26 to accept one end 27 of a rotorspring 28. The other end 29 of the rotor spring 28 is attached to afront bearing plate 44. Flats 31 are formed on the outer end of theshaft 24 to provide a loose keyed fit with the star wheel of the timedelay escapement mechanism as will be more specifically describedhereinafter. As shown most clearly in FIG. 4, a small pin 30 extendsfrom the front face of the rotor 10 to lock the rotor in its one angularposition, which is the safe position for the fuze.

The release mechanism 12 comprises a base plate 32 having a 270 slot 34formed therein and holes 36 for receiving attaching screws, a pair ofwhich are indicated by reference numerals 38. The base'plate 32 alsocontains a pair of holes 40 adapted to receive spring retaining pins 42and 43. A front bearing plate 44 forms the outer portion of the releasemechanism 12 and is attached to the base plate 32 by means of the screws38 which pass through sleeves 46 to space the plates.

A setback-actuated arming device comprising three interlockedsequentially operating leaves 48, 50, and 52 is used to arm the fuzeafter a projectile containing the fuze has been fired. As best shown inFIG. 4, the leaf 48 is restrained by a spring 54 mounted on the pin 42,while the leaf 50 is restrained by a spring 56 mounted on the pin 43.Sleeves 58 are provided on the pins 42 and 43 to prevent the springs 54and 56 from sliding and losing their engagement with the leaves 48 and50. An antireset spring 60 is attached to the base plate 32 by rivets 62to prevent the leaf 52 from rebounding to the safe position andrelatching the rotor in high acceleration shells.

The leaf 48 is pivotally mounted on a pin 64 and contains an enlargedopening 66 to allow leaf movement about this pivot. The leaf 50 ispivotally mounted on a pin 68 and contains an enlarged opening (notshown) to accomrnodate its movement around the pivot pin 68. The leaf 50also contains a pin 70 which bears against the upper corner of the leaf48 as shown in FIG. 4, when the fuze is in its safe position. The leaf52 contains a pin 72 (FIG. 2) which bears against the upper corner ofthe leaf 52 in a similar manner. An extension 74 of the leaf 52 holdsthe rotor pin 30 in the fuze safe position as shown in FIG. 4. Thus itcan be seen that the three leaves are interlocked, and when the fuze isin its safe position, the interlocking of the springs prevents arming ofthe fuze if the shell were to be dropped or mishandled.

In operation a sustained acceleration of at least 2500 g is required tocause the leaf 48 to pivot in a clockwise direction (FIG. 4) under theinfluence of the acceleration. The leaf 48 pivots around the pin 64against the force of the spring 54- and allows pivoting of the leaf 50,which is interlocked with the leaf 48, around the pin 68 against theforce of spring 56. This sequential set back of the leaves 48 and 50,removes the bias force from the leaf 52. The rotor spring 28, whichurges the rotor 10 in a clockwise direction, provides a force sufficientto overcome the restraint of the extension 74 of leaf 52 against therotor pin 30, causing the rotor 10 to rotate 270. The rotor pin 30travels this distance in the slot 34 of the base plate 32 and when rotorpin 30 is in its extreme clockwise position in the slot 34, the pin 18of the fuze detonator is in position to arm the fuze.

From the above description, it can be seen that the only delay from thetime that the projectile is fired to the time the fuze is fully armed inthe time it takes the sequential leaves 48, 50, and 52 to move fromtheir safe position to unlock the rotor 10, plus the time it takes therotor pin 30 and the rotor 10 to rotate 270. As pointed out above, inhigh muzzle velocity shells this small delay may be sufficient, but inlow muzzle velocity shells an added time delay is required.

The arming delay mechanism 14 provides the necessary arming delayrequired for the low and intermediate muzzle velocity shells. As shownin the drawings, especially FIGS. 5-7, this mechanism consistsessentially of a plate or pallet 76 and a star or escape wheel 78. InFIG. 7, it can be seen that the pallet 76 comprises a flat plate havinga large opening 80 formed therein. A pair of wedge-shaped teeth 82 and84 are formed on opposite sides of the opening 80 and project into theopening in position to engage the teeth 86 of the star wheel 78. Theteeth 86 of the star wheel are contoured to approximate an involutecurve to produce a relatively constant separating force between the starwheel 78 and the pallet 76 as the star wheel is rotated. The pallet 76has a tab 88, which isbent below the plane containing the opening 80 andcontains a hole 90 formed therein to pivotally connect the pallet to ascrew 104 secured to the front bearing plate 44. At the other end of thepallet 76 a slot 92 is formed to receive a bent over finger 94 of thestar wheel bracket 96. To increase the mass of the pallet 76 withoutincreasing the space requirement and to utilize the space present in thefuie, the other end of the pallet is bent overto form a flange 98. Thus,the center of gravity of the pallet:76 is placed relatively far from itspivot point to maximize the rotational inertia of the pallet.

The star wheel 78 is mounted in an opening 100 in the bracket 96. Anaperture 102 is provided on a lowered end 103 of the bracket 96 toaccommodate the screw 104 attaching the star, wheel-pallet assembly tothe front bearing plate 44. t A washer 106 is provided between the headof screw 104 and the lowered end 103.

The star wheel and bracket assembly is put together by placing the.upper portion of the star wheel 78 through the opening 100 in thebracket 96. The hub 110 of the star wheel 78 .fits within the opening100 and the reduced end portion 108 of the star wheel 78 is rolled overa washer 112 as shown in FIG. 6 to fix the star wheel against axialmovement while leaving it free to rotate.

A slot 116 is formed in the bore of the star wheel 78 to loosely. key itto the flats 31 on the outer end of the shaft 24..

The assembly of the time delay escapement mechanism on the fuze is asimple operation. The tab 88 of the pallet 76 is first placed on thefront bearing plate 44 with the main portion of the pallet 76 lyingabove the rotor spring 28 because the tab 88 is bent downward. Thebracket and star wheel assembly is then placed over the pallet 76 withthe star wheel 78 dropping into the opening 80. Since the end 103 of thebracket 96 is also bent downward it can be seen that the central portionof the star wheel and bracket assembly lies above the pallet 76. Thescrew 104 with the washer 106 thereon is then placed through the alignedholes 102 and 90 of the bracket 96= and the pallet 76 and screwed intothe threaded opening 107 of the front bearing plate 44. The bent overfinger 94 of the bracket 96 fits into the slot 92 of the pallet 76 .torestrict the amplitude of oscillation of the pallet. The fully assembledtime delay escapement mechanism isshown in FIGS. 5 and 6. To completethe assembly, the shaft 24, with the inner end 27 of the spring 28positioned in the slot 26, is then passed upwards through the slot 116of the star wheel 78 in the opening 80.

With the above arrangement of parts in mind, it is apparent that thepallet 76 is pivotally mounted with respect to the front bearing plate44 and the remainder of the fun to oscillate in a plane substantiallyperpendicular to the shaft 24. As seen in FIG. 5, when the rotor shaft24 rotates in the clockwise direction, urged by the rotor spring 28, theteeth 82 and 84 will engage and disengage the teeth 86 of the star wheel78 to oscillate the pallet from side to side about the screw 104.

In operating the device, the rotor spring 28 is wound by rotating therotor 10 relative to the remainder of the fuzeh As shown in FIG. 4, thefuze is held in its wound safe position by the extension 74 of the leaf52 which bears against the pin 30 to hold the rotor in place. The fuzeisthen assembled and placed into a projectile with the rotor axisperpendicular to the longitudinal axis of a the projectile and the endcontaining the screw 104 extending toward the rear of the projectile.The interlocked leaves 48, 50, and 52, keep the rotor pin 30 and thefuze itself in the safe position until the projectile is fired and largeacceleration forces sequentially depress the leaves until the final leaf52 unlatches the rotor 10 by releasing the rotor pin 30, as previouslydescribed. Thereafter,

the spring 28 with its one end 27 retained in the slot 26 in the shaft24, rotates the rotor in a clockwise direction as viewed in FIG. 4 andthe shaft 24 rotates the star wheel 78 since it is keyed to the shaft.The teeth 86 of the star wheel 78 engage the teeth 82 and 84 of thepallet 76 to oscillate the pallet. The spring 28 provides a relativelyconstant input force to drive the star wheel 78, and the repeatedreversal and re-acceleration of the pallet 76 retards the accelerationof the star wheel to produce relatively uniform motion. The relativelyheavy mass of the rotor 10 which is connected to the star wheel throughthe shaft 24 tends to slow the acceleration of the star wheel because ofits inertia. In other words, the rotors inertia tends to maintain itsrotational speed alternately helping and hindering the action of thestar wheel and pallet combination to produce a smoother rotation withoutdisturbing the actual time delay resulting from the star wheelpalletaction. Thus the time required for the input torque supplied by thespring 28 to move the rotor 10 through the desired 270 angle of rotationis added to the time delay introduced by the star wheel 78 and pallet 76to achieve the desired total time delay.

When the rotor 10 completes its 270 turn, the pin 18 of the detonator inthe rotor completes an electrical circuit which arms the fuze at adistance far enough away from the point of firing to preclude any damageif the projectile were to explode.

Thus, with the time delay escapement mechanism of the present invention,a substantial time delay is provided in a smaller space and with greatersimplicity of design than is usual for time delay mechanisms in thisrange. Only an escape wheel and an oscillating mass are provided as thedelay elements, which act in conjunction with a 270 displacement of aspring driven rotor in the fuze. A gear train is not required and therelatively long time delay is achieved by the novel pallet design inwhich the rotational inertia has been increased by completely encirclingthe escape wheel.

The simple design of the present invention enables both of the movingparts in the escapement to be mounted on a single rigid support, therebyassuring the required close control over assembly tolerances. Therequired relative motion between the two parts is achieved by looselykeying the driving element into a rectangular slot in the escape wheel.This loose keying arrangement permits normal free assembly of the rotor,while still maintaining tight tolerance control of the escapement.Further, the larger mass of the rotor provides a more favorableoperation of the time delay mechanism without an increase in the spacerequirement. The present escapement mechanism can be added to a standardproduction fuze in the available small space with little modification ofthe basic fuze design. Further, the mechanism can withstand highacceleration without any performance degradation.

This invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiment is therefore to be considered in all respects as illustrativeand not restricted, the scope of the invention being indicated by theappended claim rather than by the foregoing description, and all changeswhich come within the meaning and range of equivalency of the claim aretherefore intended to be embraced therein.

What is claimed is:

A projectile fuze having a rotor of relatively heavy mass and a shaftwith two ends extending therefrom; a plate surrounding said shaft andbeing substantially perpendicular to said shaft; an escape wheelconcentrically mounted on said shaft on one end of said shaft, saidmounting including a rectangular portion on one end of said shaft and arectangular slot formed in said escape wheel, said escape wheel having aplurality of teeth, said teeth being contoured to approximate aninvolute curve; a substantially fiat rectangularly shaped pallet membersurrounding said escapement wheel, said pallet member having two ends,one of said ends connected to said plate to allow said pallet to pivotabout said one end, the other of said ends being downwardly turned toincrease the moment of inertia of said pallet about said one end, saidpallet having two opposed pawls to mesh with said teeth of saidescapernent Wheel, said pallet further having a slot formed adjacentsaid turned down end; a bracket connected to said plate at said palletpivot point and being substantially parallel to said plate and saidpallet, said bracket having a finger thereon to cooperate with saidpallet slot to limit the pivotal amplitude of said pallet.

References Cited by the Examiner UNITED 10 BENJAMIN A. BORCHELT, PrimaryExaminer.

G. H. GLANZMAN, Assistant Examiner.

